1. Field of the Invention
The present invention relates generally to a position controller of a subject, and more particularly to a position controller for driving a camera lens by controlling its position.
2. Description of Related Art
In a motor-driven lens device, which is used for a TV camera, etc., the position of a focus lens is controlled in accordance with a position command signal outputted from a focus demand so that the focus lens can move to a target position corresponding to the operating position of the focus demand. More specifically, a position signal representing the present position of the focus lens is outputted from a potentiometer and is fed back to the position command signal outputted from the focus demand. A focus motor operates in accordance with these signals, so that the focus lens can move to the target position represented by the position command signal.
In order to improve transient response characteristics of the movement of the focus lens with respect to the operation of the focus demand, a velocity signal representing a velocity of the movement of the focus lens is usually fed back to the position command signal. The velocity signal is outputted from a tachogenerator measuring the rotational speed of the focus motor. Adjusting the feedback amount of the velocity signal enables the transient response characteristics of the movement of the focus lens with respect to the operation of the focus demand to be adjusted properly. Japanese Patent Provisional Publication No. 9-107694 discloses a servo system, which feeds back the position signal and the velocity signal to a signal for driving the motor in order to operate the motor stably.
Usually, since the transient response characteristics of the subject are greatly affected by the unevenness in electric circuits and in the frictional resistance and the viscosity resistance of a mechanical part, and the like according to the products, the circuit coefficient is adjusted by a variable resistor in some cases. Therefore, the transient response characteristics are adjusted in different manners between operators. Moreover, even the same operator may change his or her adjustment standards as time passes, and thus, the adjustment results cannot be stable.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of a position controller that automatically adjusts the transient response characteristics of the movement of the subject, whose position is controlled, to thereby prevent the unevenness in the transient response characteristics between the products, and easily readjusts the transient response characteristics even if the transient response characteristics change as time passes.
To achieve the above-mention ed object, the present invention is directed to a position controller that receives a position command signal representing a target position to move a subject and feeds back a velocity signal representing a velocity of a movement of the subject to the position command signal at a feedback gain to adjust transient response characteristics of the movement of the subject with respect to the position command signal while moving the subject in accordance with the position command signal, the position controller comprising: a test signal generator for generating a test signal of a predetermined waveform; an input switcher for switching an input to receive the test signal instead of the position command signal; a waveform reader for reading a waveform of a position signal representing a present position of the subject on the movement of the subject in response to the test signal; and a feedback gain adjuster for adjusting the feedback gain of the velocity signal so that the waveform of the position signal responsive to the test signal becomes a predetermined form.
To achieve the above-mentioned object, the present invention is directed to a position controller that receives a position command signal representing a target position to move a subject, feeds back a velocity signal representing a velocity of a movement of the subject to the position command signal at a feedback gain and feeds back a position signal representing a present position of the subject to the position command signal to adjust transient response characteristics of the movement of the subject with respect to the position command signal while moving the subject in accordance with the position command signal, the position controller comprising: a test signal generator for generating a test signal of a predetermined waveform; a test signal adder for adding the test signal to one of the position command signal and the position signal; a waveform reader for reading a waveform of the position signal on the movement of the subject in response to the test signal; and a feedback gain adjuster for adjusting the feedback gain of the velocity signal so that the waveform of the position signal responsive to the test signal becomes a predetermined form.
The test signal generator may generate the test signal of a step waveform.
According to the present invention, the input switcher switches the input to receive the test signal with a predetermined waveform (e.g., a step waveform) instead of the position command signal, or the test signal adder adds the test signal to the position command signal or the position signal. The subject is moved in accordance with the test signal, and the waveform (the response waveform) of the position signal on the movement of the subject in response to the test signal is read. The feedback gain is adjusted so that the response waveform becomes a predetermined form. It is therefore possible to set the optimum transient response characteristics of the movement of the subject automatically. This eliminates the unevenness in the transient response characteristics between the products, and the transient response characteristics can be readjusted easily even if the transient response characteristics are changed due to the changes in the products as time passes.